System and method of code telegraph signaling



Patented June 6, 1939 UNITED STATES SYSTEM AND METHOD OF CODE TELEGRAPH SIGNALING Forest L. Henderson, Stamford, Conn., assignor All America Cables,

Incorporated, New

York, N. Y., a corporation of New York Application May 29, 1937, Serial No. 145,434

6 Claims.

My invention. relates to code telegraph transmitting systems and methods, and particularly to systems utilizingv particular code combinations and the. methods of signaling utilizing such codes.

The present code. signaling systems now in use, use character elements composed of positive current impulses and negative current impulses, and space indications or periods of no current. The standard Continental cable code, for example, comprises a system inwhich dots are represented by positive current impulses, dashes by negative currentimpulses and spacings comprising no current periods, and the standard five-unit Baudot code is made up of characters represented by variousunits and combinations of? positive and negative current impulses in groups of five to indicate the various characters.

In accordance with the method and code system of my invention, characters are represented by equal. length current impulses of one polarity, positive or negative, and periods of no current. In accordance with my invention, a code composed of units representing dots and dashes as in the Continental code, is represented by current impulses and periods of no current to indicate dots and dashes, and current impulses of the opposite polarity are used to indicate spaces. For example, to reproduce the Continental code, the dots may be represented as no current periods, the dashes as negative current impulses and the character spaces as positive current impulses.

For word spacing two positive current impulses may be used.

In accordance with my system, the various characters of the five-unit or Baudot code may be a chosen combination of equal length positive or negative current impulses and spaces or periods of no current.

By use of a system and code in accordance with my invention, the total number of positive and negative impulses used may be greatly reduced in proportion to the number of spacing or no current periods. Thus, since fewer impulses and signal combinations are introduced into a line, it is easier to maintain a balance in a telegraph line.

Furthermore, since fewer impulses in sequence and signal combinations are introduced onto the line,,it is easier to shape the signals at the receiving terminals.

It is one object of my invention to so select the signal impulses that no more than two impulses in the same direction occur in sequence, thus facilitating the shaping of signals. Such facili- 5 tated shaping results in a better definition and size of the single impulses at the receiving station permitting higher speeds on submarine cables.

Another object of my invention is to provide an improved method of transmitting messages over a line, submarine cable or the like, by means l of positive and negative current impulses and periods of no current.

For transmitting with a standard equal unit code system, such as a five-unit code, my invention is very useful since it greatly facilitates the transmission of signals on a two-channel basis. In accordance with my invention, one five-unit code may be composed of positive current impulses and no current spaces or periods, and the other code may be comprised of negative current impulses and no current periods or spaces. Thus the two codes may be interspersed on a line in such a manner that no positive or negative impulses occur consecutively and therefore the line may be readily maintained in balance.

Another advantage of my invention as applied to an equal unit code is, that since currents of only one polarity are used the code may be used for transmitting signals by radio as well as by telegraph lines. When such codes are used they may likewise be used for two-channel transmission. Current impulses of the same polarity on both channels are interspersed as outlined above. Since the other parts of each character are represented by intervals or periods of no current which occur frequently during transmission, the signals are easily shaped.

It is a further object of my invention to provide a system for two-channel transmission in five units or any equi-unit code system in which the code characters comprise elements of one current polarity and no current, and the other current of opposite polarity and no current, so introduced on the line as to present at no time current impulses of like polarity in the same direction consecutively.

It is a further object of my invention to provide a method of two-channel code transmission which is readily adapted to line or radio transmission and in which the signals received are easily shaped.

It is a further object of my invention to devise an improved code for use in a Continental cable code system in accordance with the characteristics outlined above.

It is a still further object of my invention to devise a telegraph tape in accordance with the code system outlined. above.

While several specific objects have been named above, I do not intend to limit the invention to these separate objects, but intend to cover other objects and advantages which present themselves within the scope of the appended claims.

With these objects in view, a more particular description of the invention will be given in connection with the accompanying drawings, in which:

Fig. 1 diagrammatically indicates a telegraph system;

Fig, 2 illustrates a code in accordance with my invention contracted with the standard Continental cable code;

Fig. 3 illustrates perforated tape perforated in accordance with the code illustrated in Fig. 2;

Fig. 4 illustrates receiving tape upon which the signal recordings are indicated in accordance with the signals of the code shown in Fig. 2;

Fig. 5 illustrates the application of my invention to two-channel equi-unit code transmission; and

Fig. 6 illustrates another application of my invention to two-channel equi-unit code transmiss1on.

Fig. 1 shows diagrammatically a telegraph transmission system, in which ll represents a telegraph transmitter connected over line [2 to a telegraph receiver i3. The transmitter may be of any desired type, such as a manual transmitter, a tape transmitter, or any other desired form. The line [2 may be a submarine cable line or a land line, and the telegraph receiver I3 may be of any desired type, such as a syphon recorder or a printing receiver or the like. Instead of line transmission, a path of radiated energy may be used to transmit the signals.

The present Continental code is composed of three elements, namely, dots or positive current impulses, dashes or negative current impulses, and spaces or periods of no current. In this code it is well recognized that dot impulses occur more frequently than dash impulses. In accordance with my invention, the dots and dashes of the code are represented by current impulses of one polarity and periods of no current, respectively. Although either the dots or the clashes may be indicated by the current impulses, I prefer to replace the dots by no current periods and the spaces by current impulses, since in the Continental code the dots far outnumber the dashes. A space between letters is indicated as a current impulse of opposite polarity from the character impulses, and a space between words may constitute two such character spacings. The use of my method of transmission results in a smaller number of positive and negative impulses being sent through the line than in the present Continental cable code. For example, in the present systems commonly in use, if the alphabet and figures from zero to nine, inclusive, are sent, there will be 132 positive and negative impulses and 36 single spaces. In accordance with my invention. the alphabet and figures from zero to nine, inclusive, require 91 positive and negative impulses and 77 single spaces.

This contrast may be readily seen by reference to Fig. 2 of the drawings. In this figure, the code in accordance with my invention is shown in one column, in which each character together with the character spacing is indicated, and immediately to the left thereof is shown the present used standard Continental cable code. As can be readily seen by reference to this figure, my code utilizes very much fewer current impulses and no two impulses in the same direction occur consecutively. In contrast, however, in the Con tinental code as now in use, as many as five impulses in one direction may readily occur.

Although as shown in Fig. 1, the characters in accordance with my code are shown as represented by no current periods and negative impulses, and the spacings are shown as positive impulses, it should be clearly understood that positive impulses may be used together with periods of no current to indicate the characters, and negative impulses may be used to indicate spacings. Furthermore, instead of the impulses being used to replace dashes and no current periods to represent the dots, the dots may be represented by current impulses and the dashes by no current periods.

Since in a code in accordance with my invention, the ratio of positive and negative current impulses sent through the line compared to the number of space elements is much smaller than in the standard code, the use of this system on a submarine cable will result in fewer failures due to contact and instrumental trouble. Furthermore, as a result of this increased ratio of spaces to positive and negative current impulses, it is easier to balance a submarine cable. Furthermore, this balance is facilitated since the resultant code combination of letters and figures sent in sequence never produces a longer series of positive or negative current impulses in sequence than two or cross impulse combinations of more than one from positive to negative. Because of the low number of impulses in sequence applied to the line, the received impulses will not tend to drift greatly due to the charging of the line by a large number of impulses of the same polarity. Consequently, a different amount of curbing is necessary in order to shape the longer impulses and accordingly greater amplitude of the shorter impulses may be obtained. Because of this, the received signals will be more distinct and higher speeds may be obtained in submarine cable transmission.

In Fig. 3 is illustrated two strips of tape, 30 and 3|. Tape 30 is perforated in accordance with the code of the present invention, shown to the left in Fig. 2, and tape 3| is perforated in accordance with the standard Continental cable code signals. A strip of tape indicating the alphabet characters from A to J, is shown. It is readily apparent that by the use of my code the number of perforations is much less and accordingly the number of impulses impressed on the line is correspondingly reduced.

In Fig. 4 is diagrammatically illustrated a section of tape 4| upon which the received signals transmitted from tape 30 of Fig. 3, are indicated as syphon recordings. As can be readily seen in this figure, the indications recorded in accordance with my invention are quite sharply defined and uniform, and accordingly easily read.

My invention is also applicable to the use of codes having an equal number of periods to represent each character, as for example, the standard Baudot five-unit code. In accordance with my invention, the characters of the code are sent through the line as impulses of one polarity and spaces or periods of no current. This system may be readily adapted to the operation of printer telegraphs with minor changes in existing equipment.

This adaptation of my invention to a code such as the five-unit Baudot code, is useful in the operation of such codes for two-channel transmission. In Fig. 5 is illustrated one example of this two-channel multiplexing, to illustrate the applicability of my code in this system. In this figure, the characters A, Q, letter space and W are shown in one channel multiplexed with the characters P, L, K and M in the other channel. For the first channel the characters are represented by positive current impulses and no current spaces, and in the second channel as negative current impulses and periods or spaces of no current. The various characters are interspersed so that an element of one character in each channel occurs at a period intermediate the two elements of a character in the other channel. Thus spaces I, 2, 3, 4 and 5 indicate the timing of the character impulses for channel I, and correspondingly, I, 2', 3', 4 and 5' indicate the character impulse spaces for the channel II. The standard Baudot code indications are shown above and below each character for the respective channels. The dots indicate the usual marking impulses and the dashes the spacing impulses. The multiplexing in the two channels as indicated above is shown clearly at 50, in Fig. 5. It can be seen here, that the number of impulses transmitted is quite small and that no two impulses in the same direction can occur. In contrast to this multiplexing in accordance with my invention is shown the system of multiplexing when each character of both channels is represented by positive and negative current impulses. It can be readily seen that in the Baudot system it is quite possible to have a relatively large number of current impulses of the same polarity occur in sequence. Actually in transmission of the Baudot code signals in a two-channel multiplex, it is possible to have as many as ten positive current impulses in sequence. Such a large number of impulses inipressed upon the line in rapid succession clearly induces a large charging of the line and consequent distortion of the signals. In accordance with my invention, such a result is avoided since no sequence of impulses of the same polarity occurs. Furthermore, the larger number of spacings or no current points in the line reduces the total amount of current in the line and results in a further economy in use of the system.

In Fig. 6 is illustrated another example of two-channel multiplexing using only one polarity of current impulses in both channels. The same characters as those used in Fig. 5 are shown in multiplex. The code of each channel is shown as composed of positive current impulses and periods or spaces of no current in combination. The numbering of the spaces for the two channels is the same as in Fig. 5. It can be seen from observation of this figure, that no very long sequence of impulses occurs and that a relatively large amount of the pattern is composed of no current intervals. A comparison with the standard Baudot code shown in Fig. 5, clearly shows this feature. As a consequence, the signals are quite easily shaped and the balance of the line is easier to obtain, resulting in higher speed.

The relatively longer periods of spacing or no current obtained by use of a system in accordance with my invention, aids in the shaping of the signals in submarine cables, since during no current periods the cable is earthed through the transmitters. The increased earthing periods permit discharge of charges built up on the line during transmission of impulses. Accordingly, the greater number of spacing intervals permits charges to drain off more frequently, keeps the line clearer of positive or negative charges and thus any succeeding impulses are easier to shape. This principle applies as well to the systems discussed in connection with Figs. 2 and 5 as well as to Fig. 6. Since all the impulses are in the same direction in the system shown in Fig. 6, this code combination is readily adapted for radio transmission as well as line telegraphy.

While I have described particular embodiments of my invention for the purposes of illustration, it should be understood that various modifications and adaptations thereof may be made without a departure from the spirit of the invention as set forth in the appended claims.

What I claim is:

l. A method of telegraph signaling comprising, representing a set of characters by elements of two types, transmitting equal length current impulses of one polarity to represent one type of character element, using interspersed periods of no current to represent the other type of charactcr elements and so relating said impulses that no more than two impulses of the same polarity occur successively.

2. In a telegraph transmitting system, the method of signaling comprising, transmitting current impulses of one polarity with interspersed periods of no current to indicate the separate characters, and transmitting an impulse of opposite polarity to indicate a character termination or space.

3. In a telegraph transmitting system, the method of signaling comprising transmitting current impulses of one polarity with interspersed periods of no current to indicate the separate characters, transmitting an impulse of opposite polarity to indicate a character termination or space, and so relating said character current impulses that no more than two impulses of the same polarity occur in succession.

i. A method of two channel signal transmission on a single line, utilizing signal character indications on each channel composed of the same number of signal elements for each character, comprising impressing on said line one signal comprising equal length character impulses or one polarity with interspersed equal periods of no polarity for one channel, said character impulses and periods being spaced in time an amount equal to the length of one of said impulses or periods and impressing on said line a signal, comprising equal length character impulses of opposite polarity and interspersed equal periods of no polarity for said second channel, said second named impulses and periods being so impressed as to coincide with the spacing between said first named signal elements.

5. A method of two channel signal transmissicn on a single medium, using signal character indications on each channel composed of the same number of signal elements for each character, comprising transmitting on said medium signals comprising equal length character impulses of one polarity interspersed with periods of no polarity for one channel, said character impulses and periods being spaced in time an amount equal to the length of one of said impulses or periods, and impressing on said medium other signals, comprising equal length character impulses of said one polarity and interspersed equal periods of no polarity for said second channel, said second named signal impulses being impressed so as to coincide with the spacing between said first named signal elements.

6. A method of telegraph signaling using a code similar to the standard submarine cable code, consisting of signal characters represented by two types of character elements, comprising transmitting current impulses of one polarity to represent one type of character element, using no current or spacing to represent the other type of character element and transmitting current impulses of the opposite polarity to represent the spacing between characters or words of a message.

FOREST L. HENDERSON. 

